Device for receiving signals from satellite radio-navigation systems

ABSTRACT

A device for reception of the signals of satellite radio navigational systems (SRNS) GPS/Glonass comprises an input unit having two filters and an amplifier, a first signal frequency converter comprising two amplifiers and a mixer two channels (GPS and (Glonass) of the second signal frequency converter, each of which includes a filter, a mixer, a controlled-gain amplifier and a threshold device consisting of a level-controlled two-bit quantizer. The device also comprises an equipment for producing clock and heterodyne frequency signals including a unit for producing the signal of a first heterodyne frequency (frequency synthesizer) whose output is connected to the reference input of the mixer of the first frequency signal converter, and two units connected in series: the output of the first unit being connected to the connected to the reference inputs of the mixers of the second signal frequency converter and the outputs of the channels of the second converter and the output of the second frequency divider being the outputs of the device. The control inputs of gain-controlled amplifiers and threshold devices are connected to the outputs of the corresponding digital-to-analog converters whose inputs are the control inputs of the device. The device allows one to receive the SRNS GPS/Glonass signals with lettered frequencies from 0 up to 12 of the frequency bands L 1  and F 1 , respectively, using one frequency synthesizer and two frequency dividers when producing the clock and heterodyne frequencies.

TECHNICAL FIELDS

The invention relates to field of radio navigation can also be used in anavigational equipment of the users of satellite radio navigationsystems (SRNS) and, mores specifically, in radio receiving equipmentperforming simultaneous reception of signals, such as SRNS “GPS” (USA)and “Glonass” (Russian Federation).

PRIOR ENGINEERING ART

It is well known (cf. <<Onboard Devices of Satellite Radio Navigation)I. V. Kudryavtsev, I. N. Mishchenko, A. I. Volynkin, et al., Ìoscow,Transport Publishers, 1988 pp. 13-15 [1], <<Network Satellite RadioNavigation Systems”, V. S. Shebshaevich, O. O. Dmitriev, N. V.Ivantsevich et al., Moscow, Radio i Svyaz Publishers, 1993, p.35 [2].The signals, radiated by the navigational artificial satellites of theEarth (NIS)/SRNS “GPS” are radio signals modulated by the “C/A” and “P”in-phase codes: (0, π) and (+π/2, −π/2) respectively. These signals aretransmitted on two frequency bands: in a range L₁ (carrier frequency1575.42 MHz) and in a range L₂ (carrier frequency 1227.6 MHz). Signalsof the frequency band L₁ are modulated by the “C/A” and “P” codes andthe signals of the frequency band L₂ are modulated by the “P” code. Thefirst code (code “C/A”) is generated using the law of pseudo-randomsequence (PRS) with a period of 1 ms and a clock frequency of 10,023MHz; the second code (code “P”) is generated under the pseudo-randomsquence law with a period of about 7 days and a clock frequency of 10.23MHz. The “C/A” code transmitted on the frequency band L₁ and known as a“standard precision” code is open for all customers of navigationalinformation and is used in a radio navigational equipment of “standardprecision”, this class including the claimed device, while the “” codeis used in a special equipment of a higher precision.

To identify the signals radiated by various NIS3 satellites, the codedivision of the SRNS “GPS” signals is used.

In contrast to the SRNS “GPS”, in the “Glonass” pseudo-random squence(for example, cf. [2], pages 28-30), the frequency division of signalsradiated by different NIS3 is accepted. The NIS3 SRNS “Glonass” signalsare identified by the nominal value of their carrier (“lettered”)frequency lying in an assigned frequency range. Two (j=1, 2) frequencyband F₁ and F₂ are provided for the lettered frequencies. The nominalsof the lettered frequencies are formed according to the following rule:

f _(j,i) =f _(j,0) +iΔf _(j,)

ãäå:

f_(j,i) are the nominal of the lettered frequencies;

f_(j,0) is the zero lettered frequency;

i are the numbers of the letters in each band;

Δf_(j) is the interval between the lettered frequencies.

For the frequency F₁ (near 1600 MHz)−f_(1,0)=1602 MHz, Δf₁=0.5625 MHz;for the frequency F₂ (near 1240 MHz)−f_(2,0)=1246 MHz, Δf₂=0.4375 MHz.

The lettered frequencies among the functioning NIS3 satellites areallocated by a special almanac transmitted in the control informationframe.

Similarly to the “GPS” satellite radio navigation system, each NIS3 ofthe “Glonass” satellite radio navigation system signals in bothfrequency bands F₁ and F₂ The SRNS “Glonass” signals on the frequencyband F₁ are modulated by PRS codes of two types: “standard precision”(with a clock frequency of 0.511 MHz) and “high precision” (with a clockfrequency of 5.11 MHz), i.e. similarly to the “C/A” and “P” codemodulations by codes on the frequency band L₁ of the SRNS “GPS” signalsof the “Glonass” SRNS in the frequency band F₂ and similarly to the SRNS“GPS” signals in the frequency band L₂ are modulated only by thehigh-precision PRS codes. The “standard precision” code transmitted inthe frequency band F₁ is open for all users of the navigationalinformation and is used in the “standard precision” radio navigationalequipment whose class includes the claimed device, while the“high-accuracy” code is used, as a rule, in a special high-precisionequipment.

The differences existing between the signals of the SRNS “GPS” and“Glonass” due to the code division at one carrier in the SRNS “GPS” andfrequency division at several carriers defined by lettered frequenciesin the SRNS “Glonass” result in differences in technical means used forthe reception of the signals of satellite radio navigation systems forconversion them into such a form that enables the subsequent radionavigation measurements to be carried out.

For example, known from the “Global Positioning System (GPS) Receiver RFFront End. Analog-Digital Converter. Rockwell International ProprietaryInformation Order Number. May 31, 1995>>, FIG. 1 [3] is a device usedfor reception of signals from the SRNS “GPS”, comprising a low-noiseamplifier, a filter, a first mixer, a first intermediate frequencyamplifier, a quadrature mixer two quantizers for in-phase and quadraturechannels, a first heterodyne frequency oscillator (1401.51 MHz), and adivider forming of a second heterodyne frequency signal from the firstheterodyne frequency signal.

This device performs the technical task of reception and conversion ofthe SRNS “GPS” signals to a forms permitting the customer tosubsequently carry out the corresponding radio navigation measurements.The device does not allow one to receive the SRNS “Glonass” signals.

The reference book <<Satellite Radio Navigation Network Systems”, V. S.Shebshaevich, P. P. Dmitriev, H. V. Ivantsevich, et al., Ìoscow, Radio iSyaz Publishers. 1993, pp. 147-148 [2], discloses a device for receptionof the SRNS “Glonass” signals (“Single-Channel Equipment for ASN-37Customers”). The device comprises an input filter, a low-noiseamplifier, a first mixer, an intermediate-frequency amplifier, a phasedemodulator, a second mixer with phase suppression of the mirrorchannel, a limiter, a lettered-frequency synthesizer, and a localoscillator to generate signals of heterodyne frequencies. Thelettered-frequency synthesizer produces its own output signals accordingto the lettered frequencies of the SRNS “Glonass” signals beingreceived. The lettered frequency spacing provided by the synthesizer is0.125 MHz. The first heterodyne frequency signal is formed as a resultof multiplication of the output frequency signal of the synthesizer by afactor of 4, and the signal of the second heterodyne frequency is formedas a result of division of the synthesizer output frequency signal by 2.

This device performs the technical task of reception and conversion ofthe SRNS “Glonass” signals to bring them a form permitting the customerto perform the corresponding radio navigational measurements. The devicedoes not allow one to solve the problem of reception of the SRNS “GPS”signals.

In spire of differences existing between the SRNS “GPS” and the“Glonass”, they have an identical ballistic construction of the orbitalgroup of the NIS3 satellites and allocated frequency band allowing oneto state and solve the problems associated with the creation of anintegrated navigational equipment for the users of the signals of thesetwo radio navigation systems. The achievable result consists in higherreliability, authenticity and precision of definition of the objectlocation, in particular, due to a possibility of a choice of workingconstellations of the NIS3 with the best geometrical factors <<NetworkSatellite Radio Navigation Systems” (V. S. Shebshaevich, P. P. Dmitriev,N. V. Ivantsevich et al., Moscow, Radio i Svyaz Publishers, 1993, p. 160[2].

Known among such devices (<<Network Satellite Radio Navigation Systems”(V. S. Shebshaevich,, P. P. Dmitriev, N. V. Ivantsevich et al., Moscow,Radio i Svyaz Publishers, 1993, pp.158-161 [2], FIG. 9.8.”) is a deviceperforming the task of reception of the SRNS “GPS” signals in thefrequency band L₁ and the “Glonass” signals in the frequency band F₁ andconverting them to a form permitting one, using a digital processor(primary and navigational processors) to carry out the subsequent radionavigational measurements and definition of the location of the object.Such a known device comprises a frequency divider (“diplexer”)performing frequency division of the of the “GPS” and “Glonass” signals,satellite radio navigation system, band-pass filters and low-noiseamplifiers of “GPS” and “Glonass” channels, a mixer, a SHF switchfeeding the SRNS “GPS” or “Glonass” signals to the signal input of themixer, a SHF switch feeding the first heterodyne signal of the “GPS”channel or “Glonass” channel to the reference input of the mixer. Due tothe corresponding frequency shaping of the heterodyne signal the firstintermediate frequency is constant for the SRNS “GPS” and “Glonass”signals and the entire following channel of the device is realized ascommon for these signals.

A specific feature of such a device is that the reception and conversionof the SRNS signals is effected in time in succession using the sameradio channel, and this increases the time consumed for the subsequentprocessing in order to obtain the navigational information. Besides, theimplementation of the device requires a complex high-frequency switchedfrequency synthesizer to produce two different heterodyne signals usedfor conversion of the signals SRNS “GPS” and “Glonass” respectively.

Also known in the art is a device for reception of the SRNS “GPS” and“Glonass” signals described in <<Riley S., Howard N., Aardoom E., DalyP., Silvestrin P. “A Combined GPS/GLONASS High Precision Receiver forSpace Applications”/Proc. of ION GPS-95, Palm Springs, Calif., US, Sep.12-15, 1995>> pp. 835-844, FIG. 2 [4], which performs simultaneousreception of SRNS “GPS” and “Glonass” signals. The functionallycompleted part of this device solving the problem of reception of theSRNS “GPS” signals on the frequency band L₁ and the “Glonass” signals onthe frequency band F₁ and producing output signals to be used for thenavigational measurements is taken as a prior art.

The block diagram of the prior art device is shown in FIG. 1.

The device taken as a prior art, comprises (FIG. 1) an input unit 1whose input is a signal input of the device, a unit 2 of the firstsignal frequency converter comprising a first amplifier 3, a mixer 4 anda second amplifiers 5 connected in series, a first channel 6 and asecond channel 7 of the second signal frequency converter, and a module8 producing clock signals and heterodyne frequency signals said modulecomprising an independent clock generator and three units or frequencysynthesizers used for producing signals of heterodyne frequencies . (notshown in FIG. 1).

The channel 6 of the second signal frequency converter comprises afilter 9 and a mixer 10 connected in series.

The channel 7 of the second signal frequency converter comprises afilter 11 and mixer 12 connected in series.

The inputs of the filters 9 and 11 are respectively inputs of the first6 and second 7 channels of the second signal frequency converter and areconnected to the output of the amplifier 5, i.e. to the output of theunit of the first signal frequency converter 2. The input of theamplifier 3, i.e. the input of the unit 2, is connected to the output ofthe unit 1. The reference input of the mixer 4 of the unit 2 of thefirst signal frequency converter is connected to the signal output ofthe first heterodyne frequency of the module 8 formed by the signaloutputs of the first heterodyne frequency (not shown in FIG. 1). Thereference inputs of the mixers 10 and 12 of the first 6 and second 7channels of the second signal frequency converter are connectedrespectively to the outputs of the signals of the second and thirdheterodyne frequencies of the module 8, formed by the outputs of thecorresponding units producing the signals of the second and thirdheterodyne frequencies (not shown in FIG. 1).

The outputs of the mixers 10 and 12 the first of 6 and second 7 channelsof the second signal frequency converter and the output of theclock-frequency signal of the module 8 produced at the output of theclock-frequency signal generator (not shown in FIG. 1) are the outputsof the device taken as a prior art.

The prior art device operates as follows.

The SRNS “GPS” signals of the frequency band L₁ and the “Glonass”signals of the frequency band F₁ from the antenna (not shown in FIG. 1)through the input unit 1 performing frequency filtering of the signalsof the given frequency band are applied to the input of the unit of 2the first signal frequency converter.

In the unit 2 the SRNS “GPS” and “Glonass” signals of the frequency bandL₁ (F₁) are amplified in the first amplifier 3, converted by frequencyin the mixer 4 and are amplified in the second amplifier 5(intermediate-frequency amplifier).

For the first frequency conversion performed in the unit 2, device makesuse of the signal of the first heterodyne frequency f_(ã1)=1416 MHz fedfrom the corresponding output of the module 8. In the module 8 thesignal of the first heterodyne frequency f_(ã1) is synthesized with thehelp of an independent unit producing the signal of the first heterodynefrequency—the first frequency synthesizer (not shown in FIG. 1).

The SRNS “GPS” and “Glonass” signals of the frequency band L₁ (F₁)converted in the unit 2 are applied to the inputs of the first channel 6and second channel 7 of the second signal frequency converter, i.e. tothe inputs of the filters 9 and 11. Each of these filters processes thesignals of one of the SRNS, namely, the filter 9 is used for filteringthe SRNS “GPS” signals and the filter 11 is used for filtering the SRNS“Glonass”. signals.

The frequency-converted signals are filtered with the help of thefilters 9 and 11 to remove the out-of-band interference and allocated inthe systems (“GPS” and “Glonass”) in each of the channels 6 and 7 arefed to the signal inputs of the mixers 10 and 12 respectively.

For the second frequency conversion performed in the channels 6 and 7the prior art device makes use of the signals of the second and thirdheterodyne frequencies f_(ã2)=173.9 MHz and f_(ã3)=178.8 MHz synthesizedwith the help of the corresponding independent units generating signalsof the second and third heterodyne frequencies—the second and thirdfrequency synthesizers (not shown in FIG. 1) incorporated into themodule 8. Thus, the signal of the second heterodyne frequencyf_(ã2)=173.9 MHz is used for conversion of SRNS “GPS” signals in themixer 10 of the first channels 6 and the signal of the third heterodynefrequency f_(ã3)=178,8 MHz is used for conversion of SRNS “Glonass”signals in the mixer 12 of the second channels 7.

The SRNS “GPS” and “Glonass” signals converted with the help of themixers 10 and 12 are applied to the outputs of the channels 6 and 7respectively.

The SRNS “GPS” and “Glonass” signals, converted by frequency in thechannels 6 and 7, as well as the clock signal generated in the module 8with the help of an independent clock generator, for example, aquartz-controlled oscillator (not shown in FIG. 1) form the outputsignals of the devices taken as a prior art.

The output signals of the prior art device are used for performing theradio navigational measurements to obtain the corresponding navigationalinformation. In so doing the output signals are subjected to digitalprocessing, at first in 4-bit analog-to-digital converters (ADC), thenin dedicated digital filters and in a special calculator (not shown inFIG. 1). The clock signal generated in the device is used in this caseas a clock signal setting the sampling rate with time when effecting theanalog-digital conversion.

To carry out the digital processing without any loss of the navigationalinformation, the output signals of the prior art device are matched bytheir frequency and spectrum. The matching is provided by selectingdefinite clock and heterodyne frequencies. When doing this in the priorart device, the clock frequency of the next analog-digital conversion,i.e. the time-dependent sampling rate is selected as f_(ò)=57.0 MHz.Taking this frequency into account, the agreed values of heterodynefrequencies f_(ã2)=173.9 MHz and f_(ã3)=178.8 MHz for the secondfrequency conversion of signals are selected, so that the averagefrequency of SRNS “GPS” and “Glonass” signals on the second intermediatefrequency would be close to 14.25 MHz. It ensures a possibility ofdigital processing in the 4-bit ADC, in which the clock frequency isselected equal to fõ=57.0 MHz (4×14.25 MHz) and dedicated digitalfilters are used to allocate the two-bit in-phase and quadrature sampleswith a frequency of 28.5 MHz (2×14.25 MHz) [4, page 837].

Thus, in the prior art device the following signals of clock andheterodyne frequencies are generated: a clock frequency of 57.0 MHz, afirst heterodyne frequency of 1416 MHz, a second heterodyne frequency of173.9 MHz, the third heterodyne frequency of 178.8 MHz.

The generation of the above signals of heterodyne frequencies is carriedout in the prior art device by means of local oscillators whosecomplexity is stipulated by the fact that none of the heterodynefrequencies can be obtained from another heterodyne frequency used inthe prior art device by simple multiplication or division. Therefore,the heterodyne frequencies are synthesized with the help of threeindependent synthesizers of heterodyne frequencies which are built-inthe module 8 (not shown in FIG. 1), each of which represents anindependent radio component whose complexity is stipulated by the highrequirements imposed on the stability of the synthesized frequencies(relative frequency instability is 10⁻¹¹ to 10⁻¹² per second. [5]),since this has a significant effect on the output characteristics of thereceiving device as a whole.

The use of complex heterodyne equipment (three independent frequencysynthesizers) in the prototype device and a high clock frequency (57.0MHz) complicates the digitizing equipment and makes it difficult to usethe prior art device as a portable (pocket) receiver for determining theposition by means of the SRNS “GPS” and “Glonass” signals

In this connection, the task of simplifying the equipment generating theclock and heterodyne signals, for example, a decrease of the number offrequency synthesizers is obvious. The possibility of creation ofsmall-size receiver-indicators convenient for use and defining thelocation by the SRNS “GPS” and “Glonass” signals depends on the solutionof this problem, and this is especially important, for example, for thecase of portable (pocket) receiver-indicators intended for general useby a wide circle of customers.

DISCLOSURE OF THE INVENTION

The basic object of the claimed invention is to the create a devicerealizing simultaneous reception and conversion of the SRNS “GPS”signalson the frequency band L₁ and “Glonass” on the frequency band F₁ usingone common synthesizer for producing the signals of clock and heterodynefrequencies, the clock frequency of the produced signal being matched tothe spectrum of the SRNS “GPS” and “Glonass” signals converted in thedevice.

This object of the invention is attained by providing a device forreception of signals of satellite radio navigation systems comprising ainput whose input is a signal input of the device and the output signalsare fed to the first frequency converter comprising a first amplifierwhose input is an input of the unit of the first signal frequencyconverter, a mixer and a second amplifier connected in series to theoutput of the second amplifier of the first frequency converter, a firstchannel and a second channel of the second signal frequency converter,each of which comprises a filter whose input is an input of thecorresponding channel of the second signal frequency converter and amixer connected in series, a generator generating a signal of the firstheterodyne frequency, and a module producing the signals of the clockand heterodyne frequencies. The signal output of the first heterodynefrequency is connected to the reference input of the mixer of the firstsignal frequency converter and signal output of the second heterodynefrequency is connected to the reference input of the mixer of the firstchannel of the second signal frequency converter; the outputs of thechannels of the second signal frequency converter and the signal outputof the clock and heterodyne frequencies are the outputs of the claimeddevice, the unit producing the signal of clock and heterodynefrequencies is connected to the output of the unit producing signals ofa first heterodyne frequency; units for the first and a second frequencydivision, respectively, by eight and by 2^(N), where N=1, 2, 3. Theoutputs of this unit make, respectively, a signal output of the secondheterodyne frequency and a signal output of the clock frequency of theunit producing the signals of the clock and heterodyne frequencies, inwhich case said signal output of the second heterodyne frequency isconnected also to the reference input of the mixer of the second channelof the second signal frequency converter, while in each of the channelsof the second signal frequency converter the mixer output is connectedto the output of the channel through an controlled-gain amplifier and athreshold device connected in series.

In the device for reception of signals of satellite radio navigationsystems the input unit in made as a module including a first band-passfilter, a gain-controlled amplifier and a second band-pass filterconnected in series; the control inputs of the gain-controlledamplifiers and control inputs of the threshold devices of both channelsof the second signal frequency converter are connected to the outputs ofthe corresponding digital-to-analog converters whose inputs are controlinputs of the device, and the threshold devices of both channels of thesecond signal frequency converter are made in the form oflevel-controlled two-bit quantizers.

PREFERABLE EMBODIMENT OF THE INVENTION

The essence of the claimed invention, a possibility of its realizationand industrial use are illustrated in the drawings and frequencydiagrams shown in FIGS. 1-5, in which:

FIG. 1 is a block diagram of the device taken as a prior art;

FIG. 2 is a block diagram of the claimed device in one of possibleembodiments of the invention;

FIG. 3 shows the frequency diagrams illustrating the allocation on thefrequency bands of the SRNS “GPS” signals being received in thefrequency range L₁ and “Glonass” signals in the frequency range F₁effected in the claimed device before performing the first frequencyconversion;

FIG. 4 shows the frequency diagrams illustrating the allocation of thefrequency bands of the SRNS “GPS” signals and “Glonass” signals afterthe first frequency conversion in the claimed device;

FIG. 5 shows the frequency diagrams illustrating the allocation of thefrequency bands of the SRNS “GPS” signals (FIG. 5a) and “Glonass” (FIG.5b) after the second frequency conversion in the claimed device.

As seen from FIG. 2, the claimed device comprises an input unit 1 whoseinput is a signal input of the device, a unit 2 which is a firstfrequency converter used to covert the signals. This first frequencyconverter comprises a first amplifier 3, a mixer 4 and a secondamplifiers 5 connected in series; a first channel 6 and a secondchannels 7 of the second signal frequency converter, as well as a unit 8generating signals of the clock and heterodyne frequencies. The channelof second frequency converter 6 comprises a filter 9 and a mixer 10connected in series; the channel of the second frequency converter 7comprises a filter 11 and a mixer 12 connected in series.

In the claimed device in the channel of the second frequency converter 6the output of the mixer 10 through a controlled-gain amplifier 13 isconnected to the input of a threshold device 14 whose output is anoutput of the channel 6, i.e. the output of the SRNS “GPS” signals.

In the channel of second frequency converter 7 the output of the mixer12 through a controlled-gain amplifier 15 is connected to the input of athreshold device 16 whose output is an output of the channel 7, i.e. theoutput of the SRNS “Glonass” signals.

In this embodiment of the claimed device the threshold devices 14 and 16of both channels 6 and 7 of the second frequency converter are made inthe form of the two-bit level quantizers.

In the embodiment being discussed the input unit 1 in made in the formof a first band-pass filter 17, an amplifier 18 and a second band-passfilters 19 connected in series.

In the claimed device the module 8 generating the signals of clock andheterodyne frequencies in made in the form of a series circuitcomprising a unit 20 producing the signal of the first heterodynefrequency (synthesizer of signals of the first heterodyne frequency), afirst unit 21 dividing the frequency band by 8 and a second unit 22dividing the frequency band by 2^(N), where N=1, 2, 3.

The unit 20 producing the signals of the first heterodyne frequency inthis embodiment of the claimed device in made in the form of a referencefrequency generator 23 of a phase-lock unit 24 and a voltage controlledgenerator 25 connected in series. The output of the generator 25, whichis an output of the unit 20, is also connected to the second input ofthe phase lock unit 24 whose third input is an input for the controlsignals fed from the digital processing unit—the navigational digitalprocessor (not shown in FIG. 2).

In the module 8 the output of the unit 20 is an output of the signal ofthe first heterodyne frequency, the output of the unit 21 is an outputof the signal of the second heterodyne frequency, and the output of theunit 22 is an output of the clock signal.

The inputs of the filters 9 and 11, being inputs of the first channel 6and the second channel 7 of the second signal frequency converter,respectively, are connected to the output of the amplifier 5, that is tothe output of the unit 2 of the first signal frequency converter.

The input of the amplifier 3, being an input of the unit 2, is connectedto the output of the unit 1, i.e. to the output of the filter 19.

In the claimed device, the module 8 generating the signals of clock andheterodyne frequencies is made in the form of a series circuitcomprising a unit 20 producing the signal of the first heterodynefrequency (synthesizer of signals of the first heterodyne frequency), afirst unit 21 dividing the frequency band by 8 and a second unit 22dividing the frequency band by 2^(N), where N=1,2,3.

The reference inputs of the mixers 10 and 12 of the channels 6 and 7 ofthe second frequency converter are connected to the signal output of thesecond heterodyne frequency device 8, that is to the output of the unit21 dividing the frequency by eight.

The control inputs of the amplifiers 13 and 15 in the embodiment inquestion are connected to the outputs of the correspondingdigital-to-analog converters (DAC) 26 and 27 whose inputs are digitalsignal inputs for automatic gain control (AGC) of the amplifiers.

The control inputs of the threshold devices: two-bit quantizers bylevels 14 and 16 in the embodiment under discussion are connected to theoutputs of the corresponding DAC 28 and 29 whose inputs are digitalsignal inputs for automatic balancing of the threshold of the thresholddevices.

The inputs the DAC 26-29 are control inputs of the device.

The outputs of the channels 6 and 7 and the clock signal output of themodule 8 are the outputs of the claimed device.

INDUSTRIAL APPLICABILITY

The claimed device is realized on the basis of standard, seriallyproduced radio electronic components.

Thus, the input unit 1, comprising the band-pass filters 17, 19 and theamplifier 18, can be made, for example, using standard ceramic filtersperforming function of band-pass filters, and an amplifier such asMGA-87563 of the HEWLETT-PACKARD corporation

The unit 2 comprising the first signal frequency converter, amplifier 3and mixer 4 jointly with the generator 25 included into structure of theunit 20, can be base, for example, on a chip such as MC13142 of theMOTOROLA corporation, while the amplifier 5 of the unit 2 may be builtaround a chip such as UPC2715 of the NEC company.

The filters 9 and 11 included into the channels 6 and 7 of the secondfrequency converter can be made in the form of band-pass filters onsurface acoustic waves (SAW), for example, as described in [6, pages217-220]; mixers 10, 12 and controlled-gain amplifiers 13, 15 may bebased, for example, on chips type UPC2753 of the NEC company, andthreshold devices 14, 16 (two-bit level quantizers) may use doublecomparators type MAX 962 of the MAXIM corporation.

The digital-analog converters 26-29 can be built around, for example,quad eight-bit DAC such as MAX533 of the MAXIM corporation.

The reference frequency generators 23 included into the unit 20 can bemade in the form of a quartz-controlled oscillator producing a signalwith a frequency of 15,36 MHz. In particular, there can be used aquartz-controlled thermally compensated generator, type TEMPUS-LVA ofthe MOTOROLA corporation. The phase lock unit 24 included into the unit20 can be made, for example, using a chip such as LMX2330 of theNATIONAL SEMICONDUCTOR corporation, which comprises input frequencydividers, reference frequency dividers, a phase detector, a buffer andinternal registers ensuring operation of the closed loop phase lock. Thefrequency division factor of said dividers of the unit 24 are set byexternal signals or digital codes fed to the third input of the unit 24from digital signal processing device—a digital navigational processor(not shown in FIG. 2). The division factors of the said dividers are setproceeding from a selected relation between the reference frequency(15,36 MHz) and the first heterodyne frequency (1413,12 MHz). Thedivision factor of the reference frequency is 8, the frequency divisionfactor of the generator 25 is 736, the matching frequency is 1.92 MHz.The phase detector of the unit 24 produces voltage corresponding to thephase error at the output of the frequency dividers of the generator 25(chips MC13142 of the MOTOROLA CORPORATION) and the reference frequencyproduced by the generator 23, which is used for adjusting the frequencyof the generator 25 with the help of its control element—varicap. Thisvoltage is applied to the varicap of the generator 25 through anRC-filter included into the unit 24 and providing the transfercharacteristic of the phase lock closed loop with a band of 50 kHz. Sucha design of the unit 20 generating the signals of the first heterodynefrequency corresponds to a standard scheme of frequency synthesizers,for example, [7, page pages 2-3 . . . 2-14, FIG. 6].

The units 21 and 22 dividing the frequency by eight and by 2^(N), whereN=1, 2, 3, can be built around standard frequency dividers, for example,MC12095 of the MOTOROLA corporation, operating in a mode of division by2, and frequency dividers MC12093 of the MOTOROLA corporation operatingin the mode of division by 4.

The operation of the claimed device will be considered on an example ofreception and conversion of the SRNS “GPS” and “Glonass” signals for acase, when in SRNS “Glonass” signals lettered frequencies from i=0 i=12are used. These lettered frequencies are used according to the“Interface Control Document” [8].

The claimed device operates as follows.

The SRNS “GPS” and “Glonass” signals on the frequency band L₁ (F₁)signals received by the antenna (not shown in FIG. 2) are applied to theinput of the first band-pass filter of the input units 1, performing thefrequency filtering of the signals of the given frequency band. The SRNS“GPS” signals in this case occupy a frequency band having a widthΔF=8,184 MHz and the SRNS “Glonass” signals occupy a frequency bandhaving a width ΔF=10.838 MHz The frequency bands of the SRNS “GPS” and“Glonass” signals are not intersected. The position on the frequencybands occupied on an frequency axis by the SRNS “GPS” and “Glonass”signals is in this case shown in FIG. 3, where the frequency band of theSRNS “GPS” signals is within 1571.328-1579.512 MHz and frequency band ofSRNS “Glonass” signals is within 1599.956-1610.794 MHz.

From the output of the filter 17 the SRNS “GPS” and “Glonass” signalsare fed through the amplifier 18 to the input of the filter 19, which inthis case can be made similarly to the filter 17 and have the sameamplitude-frequency characteristic. The use of two band-pass filters 17and 19 interconnected through the amplifier 18, allows one to realizethe necessary characteristics of the input unit 1 on the frequencyselectivity and signal-to-noise ratio with a common passband, forexample, 40 MHz.

From the output of the unit 1 the SRNS “GPS” and “Glonass” signals onthe frequency band L₁ (F₁) are fed to the input of the unit 2 of thefirst signal frequency converter, where they are amplified in the firstamplifier 3, frequency-converted in the mixer 4 and amplified in thesecond amplifier 5 (intermediate frequency amplifier).

For the first frequency conversion performed in the mixer 4 of the unit2 of the claimed device, the signal of the first heterodyne frequencyfã₁=1413.12 MHz, synthesized in the unit 20 with the help of thegenerator 25 and phase lock unit 24 from the reference signals with afrequency of 15.36 MHz generated by the reference frequency generator 23is used.

As a result of the first frequency conversion, the position on thefrequency bands occupied by the SRNS “GPS” and “Glonass” signals on thefrequency axis is changed as shown in FIG. 4, where the frequency bandof the SRNS “GPS” signals is allocated in a range of 158.208-166.392MHz, and the band of SRNS “Glonass” signals is allocated in a range of186.386-197.674 MHz.

The choice of the first heterodyne frequency (fã₁=1413.12 MHz) iseffected so that the associated second heterodyne frequency(fã₂=⅛×fã₁=176.64 MHz) is located between the upper boundary on thefrequency band of the converted SRNS “GPS” signals and the low boundaryon the frequency band of the converted SRNS “Glonass” signals (FIG. 4).

The SRNS “GPS” and “Glonass” signals from the output of the amplifier 5are converted in the unit 2 and fed to the inputs of the first channel 6and second channel 7 of the second signal frequency converter, i.e. tothe inputs of the filters 9 and 11. Each of these filters performs theband filtering of the signals corresponding to SRNS, namely: the filter9 filters the SRNS “GPS” signals and filter 11 filters the SRNS“Glonass” signals. The filters 9 and 11 have passbands of 8.2 MHz and10.8 MHz, respectively, and base frequencies of 162.3 MHz and 192.3 MHzrespectively.

The (“GPS” and “Glonass”) signals filtered from out-of-band interferencewith the help of the filters 9 and 11 and divided by frequency in eachof the channels 6 and 7 are fed to the signal inputs of the mixers 10and 12 respectively

For the second frequency conversion performed in the mixers 10 and 12 ofthe channels 6 and 7, the claimed device makes use of the signal of thesecond heterodyne frequency fã₂=176.64 MHz formed with the help of theunit 21 dividing the frequency by eight from the signal of the firstheterodyne frequency synthesized by the unit 20.

As a result of the second frequency conversion the position of thefrequency bands occupied by the SRNS “GPS” and “Glonass” signals, on thefrequency axis varies as shown in FIG. 5, where FIG. 5à is the frequencyband of the SRNS “GPS” signals (10.248-18.432 MHz), FIG. 5b is thefrequency band of the SRNS “Glonass” signals (10.196-21.034 MHz).

The SRNS “GPS” and “Glonass” signals, converted with the help of themixers 10 and 12, in each of the channels 6 and 7 of the secondfrequency converter are amplified by the controlled-gain amplifiers 13and 15 and then are subjected to three-level (two-bit) conversion in thethreshold devices 14 and 16, which are two-bit level quantizersproviding required output signals of the claimed device.

In the claimed device use is made of a digital gain control of theamplifiers 13 and 15 with the help of DAC 26 and 27, receiving thedigital control signals from a digital processing device or a digitalnavigational processor (not shown in FIG. 2). The gain control of theamplifiers 13 and 15 is necessary for maintaining a define level of thesignals fed to the threshold devices 14 and 16.

In the claimed device there is also used digital threshold balancing ofthreshold devices 14 and 16 by means of two-bit level quantizers basedon DAC 28 and 29 which also receive digital control signals from adigital processing device or digital navigational processor (not shownin FIG. 2). The balanced thresholds of the threshold devices 14 and 16compensate the scatter of the parameters and temperature fluctuation oftheir passive and active elements.

The digital control signals are fed to the DAC 26-29 from a digitalprocessing device or digital navigational processor (not shown in FIG. 2through a serial interface.

The output signals of the claimed device generated as described aboveare subjected to digital processing in the navigational digitalprocessor (not shown in FIG. 2) for the purpose of obtaining thenavigational information. This digital processing at the initial stageincludes quantization (digitization) of the output signals of thechannels 6 and 7 on time with a clock frequency f_(T) determined by theclock signal generated by the unit 22 from the output signals of theunit 21, that is from the signal of the second heterodyne frequencyfã₂=176.64 MHz, by dividing the frequency fã₂ by 2^(N), where N=1, 2, 3.When N=3, the clock frequency is minimum and makes a value f_(T)=22.08MHz.

In order to perform the digitization on time and without loss of thenavigational information, the converted the SRNS “GPS” and “Glonass”signals and the clock signal are matched with each other, namely: thevalue of the clock frequency f_(T) and the value of the frequency bandof the converted SRNS “GPS” and “Glonass” signals are in an approximateratio of 2^(N), where N=1, 2, 3.

In view of above, in the claimed device the following signals ofheterodyne and clock frequency are generated: a first heterodynefrequency fã₁=1413.12 MHz, a second heterodyne frequency fã₂=176.64 MHzand a clock frequency f_(T)=fã₂: 2^(N)=176.64: 2^(N), where N=1, 2, 3.In this case, the signal of the second heterodyne frequency and theclock signal are obtained from the signal of the first heterodynefrequency by means simple sequential division of this frequency by eightand by two 2^(N), where N=1, 2, 3 with the help of the units 21 and 22.

Thus, the claimed device performs the technical task of simultaneousreception and conversion of the SRNS “GPS” and “Glonass” signals withlettered frequencies from i=0 up to i=12 of the frequency band L₁ (F₁)using one common frequency synthesizer (unit 20) for producing thesignals of clock and heterodyne frequencies. In this case, the frequencyof the generated clock signal is matched with the spectrum of the SRNS“GPS” and “Glonass” signals to be converted in the device.

INDUSTRIAL APPLICABILITY

The proposed structure of the device provides a possibility itsrealization using standard radio electronic components ofindustrial-scale production. This fact essentially simplifies theimplementation of the device in terms of serial production and createsthe premises for using the claimed device in portablereceiver-indicators defining the location by the SRNS “GPS” and“Glonass” signals and intended for general use by a wide circle ofusers.

From what is considered above, it is clear that the claimed invention isfeasible, industrially applicable, provides a decision of theabove-mentioned technical task and has perspectives on using it inportable receiver-indicators operating simultaneously on the SRNS “GPS”and “Glonass” signals and realizing the standard precision ofnavigational site locations.

REFERENCES

1. “Onboard Devices of Satellite Radio Navigation”, I. V. Kudryavtsev,I. N. Mishchenko, A. I. Volynkin at al., Ìoscow., Transport, 1988.

2. “Network Satellite Radio Navigational Systems”, V. S. Shebshaevich,P. P. Dmitriev, N. V. Ivantsevich et al., Ìoscow, Radio i Svyaz, 1993.

3. “Global Positioning System (GPS) Receiver RF Front End. Analog-DigitlConverter”, Rockwell International Proprietary Information Order Number.May 31, 1995.

4. Riley S., Howard N., Aardoom E., Daly P., Silvestrin P. “A CombinedGPS/GLONASS High Precision Receiver for Space Applications”, Proc. ofION GPS-95, Palm Springs, Calif., US, Sep. 12-15, 1995, p.835-844.

5. Moses I. “Navstar Global Positioning System oscillator reguirementsfor the GPS Manpack”, Proc. of the 30th Annual Frequency ControlSympos., 1976, pp.390-400.

6. “Radio Receivers”, Bankov V. N. Banks Â.Í., Barulin L. G.,Zhodzhinsky M. I. et al., Íoscow, Radio i Svyaz, 1984.

7. Professional Products IC Handbook, May 1991. GEC PlesseySemiconductors.

8. “Global Navigational Satellite System”. The control document (thirdedition). The coordination scientific-information Center ÂÊÑ ÌÎ

Russian Federation. Moscow, 1995.

What is claimed is:
 1. A device for reception of signals of satellite radio navigation systems comprising: an input unit having an input, which is a signal input of the device, and an output; a first signal frequency converter having the output of the input unit connected thereto, said first signal frequency converter comprising a first amplifier, whose input is an input of the first frequency converter, a mixer and a second amplifier connected in series; a second signal frequency converter comprising a first channel and a second channel, wherein the output of the second amplifier of the first signal frequency converter is connected to the first channel and the second channel of the second signal frequency converter, the first channel and the second channel each comprising a filter, whose input is an input of the corresponding channel of the second signal frequency converter, and a mixer; and a first unit which produces signals of a clock and heterodyne frequencies and has an output of a signal of a first heterodyne frequency connected to a reference input of the mixer of the first signal frequency converter, and an output of a signal of a second heterodyne frequency connected to a reference input of the mixer of the first channel of the second signal frequency converter, wherein outputs of the first and second channels of the second signal frequency converter and output of the signal of the clock frequency are outputs of the device, the first unit comprises: a second unit, the second unit producing the signals of the first heterodyne frequency; and a first and a second frequency dividers connected to an output of the second unit, the first and second frequency dividers being connected in series and frequency dividing by eight and by 2^(N), respectively, where N=1, 2, 3, outputs of the first and second frequency dividers making up, respectively, the output for the signal of the second heterodyne frequency and the output for the signal of the clock frequency of the first unit producing the signals of the clock and heterodyne frequencies, the signal output of the second heterodyne frequency is connected to a reference input of the mixer of the second channel of the second signal frequency converter, and in each of the first and second channels of the second signal frequency converter the output of the mixer is connected to the output of the channel through a controlled-gain amplifier and a threshold device connected in series.
 2. The device as claimed in claim 1, wherein the input unit comprises a first band-pass filter, an amplifier and a second band-pass filter connected in series.
 3. The device as claimed in claim 1, wherein control inputs of the gain-controlled amplifiers and control inputs of the threshold devices of the first and second channels of the second signal frequency converter are connected to outputs of corresponding digital-to-analog converters whose inputs are control inputs of the device.
 4. The device as claimed in claim 1, wherein the threshold devices of the first and second channels of the second signal frequency converter are in a form of level-controlled two-bit quantizers. 